Paper and Printing Failures (I)

First, the paper caused by printing failure (a) the quality of the system factors Paper coating and sizing Non-uniform paper consists of fibers, and the paper surface cannot be completely uniform. Therefore, it is necessary to coat the surface of the paper with a layer of inorganic mineral pigments and a binder to improve the surface quality of the paper. The finer the particles, the smoother and finer the coated surface, and the rougher the surface.
In addition, in order to reduce the phenomenon of de-powdering and hair loss of paper, a surface sizing process is adopted in papermaking, that is, a layer of adhesive is applied on the surface of the paper to improve the surface strength and gloss of the paper. Due to the high printing speed of modern printing presses, the ink and the paper surface are instantly disengaged, and the ink has a large pulling force on the surface of the paper, and it is required that the coating sizing on the paper surface be uniform.
2. Paper flatness is poor The flatness of the paper is poor. The specific performance is:
1 Bubble formation on the surface of the bubbling paper is due to the fact that when the paper passes through the heat dryer, the water escaping speed on the surface of the paper is lower than the speed produced by the internal vapor of the paper, and the internal vapor is formed under pressure in the paper.
2 There is a hole in the paper surface, pulp block This is formed in the paper screening and purification process. The hole is formed after the paper is formed, and impurities are peeled off from the paper surface. Large holes can produce shutdowns or produce waste at the time of printing; large, hard blocks of paste can damage the plates and erasers during printing, which can affect the printing job.
To avoid the above phenomenon, the main measures taken are:
The 1 paper dryer has good ventilation equipment so that water vapor evaporated from the paper can be quickly discharged outside the house.
2 Perform secondary drying to accelerate moisture removal.
3 Carefully screen and purify the pulp.
(b) Water content of paper 1. Cause analysis 1. Paper from the paper mill to the printing plant until the printing process, due to transportation and storage, use and other aspects of the ambient temperature and humidity changes, combined with the paper structure of the fiber containing hydroxyl groups can form hydrogen bonds, when wet hydrophilic Swelling occurs; syneresis shrinks when dry. The paper around the water, dehydration speed faster than the center of the paper, so that the center of the paper and the surrounding water content is uneven, resulting in the paper's pressing and lotus leaf phenomenon, if used for printing, one is to lead to overprint printing products are not allowed; Second, Finished product wrinkles, causing waste products. The specific performance is:
1 tight edge phenomenon: the paper is in a dry environment, the phenomenon of dewetting occurs, that is, the center of the wet speed paper is less than the paper around, so that the paper around the tension, the formation of a tight edge phenomenon.
2 lotus leaf phenomenon: the paper is in the air and humidity environment, hygroscopic phenomenon occurs, that is, the moisture absorption stretches faster around the center of the paper, the paper forms a lotus leaf.
2. Remedy 1 When the paper has a tight edge phenomenon, sprinkle more water around the paper stack or the machine to re-absorb water around the paper and balance the moisture content of the paper so that the paper can be flattened.
Paper is dried in an environment where the relative humidity is 6 to 8% higher than in the press room.
2 When the paper appears flounces, the paper can be knocked manually by hand to knock out the creases with a width of about 1cm and a length of about 10cm, so as to increase the stiffness of the paper so as to facilitate the paper feeding;
In severe cases, it is necessary to re-hang the paper. (To be continued)